Abies firma is a medium-sized to large evergreen coniferous tree growing to 50 m tall and 2 m in trunk diameter, with a broad conical crown of straight branches rising at an angle of about 20° above horizontal. The bark is scaly grey-brown, with resin blisters on young trees. The shoots are grooved, buff to grey-brown, glabrous or finely pubescent. The leaves ("needles") are flattened, 2-5 cm long and 2-4 mm broad, spread at nearly right angles from the shoot; the apex is sharp, bifid (double-pointed) on the leaves of young trees, single-pointed on mature trees. They are bright green above, and greyish-green below with two broad stomatal bands. The cones are 7-15 cm long by 3-5 cm wide, green maturing yellow-brown, tapering to a 2-3 cm broad bluntly rounded apex. The scale bracts are exserted 3-6 mm, triangular. The seeds are 7-9 mm long with a wedge-shaped wing 1.5 cm long, are released after the cones disintegrate at maturity in October.